Semiconductor devices are commonly found in modern electronic products. Semiconductor devices vary in the number and density of electrical components. Discrete semiconductor devices generally contain one type of electrical component, e.g., light emitting diode (LED), small signal transistor, resistor, capacitor, inductor, and power metal oxide semiconductor field effect transistor (MOSFET). Integrated semiconductor devices typically contain hundreds to millions of electrical components. Examples of integrated semiconductor devices include microcontrollers, microprocessors, charged-coupled devices (CCDs), solar cells, and digital micro-mirror devices (DMDs).
Semiconductor devices perform a wide range of functions such as signal processing, high-speed calculations, transmitting and receiving electromagnetic signals, controlling electronic devices, transforming sunlight to electricity, and creating visual projections for television displays. Semiconductor devices are found in the fields of entertainment, communications, power conversion, networks, computers, and consumer products. Semiconductor devices are also found in military applications, aviation, automotive, industrial controllers, and office equipment.
Semiconductor devices exploit the electrical properties of semiconductor materials. The atomic structure of semiconductor material allows its electrical conductivity to be manipulated by the application of an electric field or base current or through the process of doping. Doping introduces impurities into the semiconductor material to manipulate and control the conductivity of the semiconductor device.
A semiconductor device contains active and passive electrical structures. Active structures, including bipolar and field effect transistors, control the flow of electrical current. By varying levels of doping and application of an electric field or base current, the transistor either promotes or restricts the flow of electrical current. Passive structures, including resistors, capacitors, and inductors, create a relationship between voltage and current necessary to perform a variety of electrical functions. The passive and active structures are electrically connected to form circuits, which enable the semiconductor device to perform high-speed calculations and other useful functions.
Semiconductor devices are generally manufactured using two complex manufacturing processes, i.e., front-end manufacturing, and back-end manufacturing, each involving potentially hundreds of steps. Front-end manufacturing involves the formation of a plurality of die on the surface of a semiconductor wafer. Each semiconductor die is typically identical and contains circuits formed by electrically connecting active and passive components. Back-end manufacturing involves singulating individual semiconductor die from the finished wafer and packaging the die to provide structural support and environmental isolation. The term “semiconductor die” as used herein refers to both the singular and plural form of the words, and accordingly, can refer to both a single semiconductor device and multiple semiconductor devices.
One goal of semiconductor manufacturing is to produce smaller semiconductor devices. Smaller devices typically consume less power, have higher performance, and can be produced more efficiently. In addition, smaller semiconductor devices have a smaller footprint, which is desirable for smaller end products. A smaller semiconductor die size can be achieved by improvements in the front-end process resulting in semiconductor die with smaller, higher density active and passive components. Back-end processes may result in semiconductor device packages with a smaller footprint by improvements in electrical interconnection and packaging materials.
The packaging of a semiconductor die is among the final steps in the long chain of processes for manufacturing semiconductor integrated circuits. Semiconductor die packaging has a direct impact on the die performance and reliability as well as the performance and reliability of electronic devices in which the die are incorporated. In many instances, packaging involves mounting the semiconductor die to a substrate, e.g., in flipchip arrangement, with electrical interconnect, and then encapsulating the die in a manner that seals and protects the die from the external environmental contaminants. Packaging also can facilitate the conduction of heat away from the die during operation.
FIG. 1a shows a semiconductor die 10 from a semiconductor wafer with contact pads 12 formed over active surface 14 of the die. An under bump metallization (UBM) layer 16 is formed over contact pads 12. Semiconductor die 10 are formed at wafer fabrication facilities. Bumps 18 are formed over UBM layer 16. Substrate 20 includes conductive traces or bond pads 22. Semiconductor die 10 is brought in proximity of substrate 20 with bumps 18 contacting bond pads 22. Bumps 18 are reflowed to metallurgically and electrically connect semiconductor die 10 to substrate 20, as shown in FIG. 1b. Semiconductor die 10 are mounted to substrate 20 at a die assembly facility. Bumps 18 typically have a height of 70-100 micrometers (μm) and width or diameter of 100-125 μm, which imposes limits on the pitch and input/output (I/O) count or density for a given die size.